Tunable three-level Nd:YAG CW laser with three lowest wavelengths at 869, 875, and 878 nm

We present a tunable three-level Nd:YAG laser using a birefringent filter (BF) based on the F-4(3/2)-I-4(9/2) transition, generally used for a 946 nm emission. Three-level Nd:YAG laser was performed at three different laser wavelengths of 869 (pure-three-level), 875 (pure-three-level), and 878 nm (quasi-three-level). Within three wavelengths, the 875 and 878 nm were demonstrated for what is believed to be the first time. The highest output power of 1.21 W was achieved at 869 nm with a slope efficiency of 9.9%. Moreover, a continuous-wave (CW) simultaneous dual-wavelength Nd:YAG laser at 875 and 878 nm was also demonstrated for the first time.